In design, there three corresponding relationships between source ends and destination ends: one-to-one, one-to-many and many-to-one. The relationship between multiple source ends and one destination end is the most complicated, and a circuit structure thereof is shown in FIG. 1. The multiple source ends are connected to the destination end through a multiplexer (MUX), and a set of arbitration mechanism is required to assist operation, so as to guarantee time-sharing exchanging of data between the multiple source ends and the destination end.
The basic principle of the arbitration mechanism is to generate gating signals based on request signals of each source end according to a certain arbitration principle such that time-sharing exchanging of data between the corresponding source end and the destination end can be achieved. The arbitration principle is generally classified into three types: fixed priority level, cyclic priority level and polling priority level.
1. Fixed priority level. As shown in FIG. 2, the priority level of each source is specified. In this figure, 0 represents the highest priority level, and 2 represents the lowest priority level. Whenever arbitration is performed, requests of the source ends are responded in an order of priority levels from high to low. For example, when source 0 and source 2 request data simultaneously, according to the priority level rule, the priority level of source 0 is higher than that of source 2, thus requests of source 0 are firstly responded. After the requests of source 0 have been responded, only when it is determined that both source 0 and source 1 have no request, requests of source 2 will be responded.
2. Cyclic priority level. As shown in FIG. 3, whenever a source end with the highest priority level is responded, this source end will be set as the lowest priority level and priority levels of the remaining source ends are increased in sequence such that each source end can obtain an equal priority level in cycles. In this figure, 0 represents the highest priority level, and 2 represents the lowest priority level. Whenever arbitration is performed, requests of the source ends are responded in an order of current priority levels from high to low. For example, when source 0 and source 2 request data simultaneously, firstly the priority level of source 0 is set as 0 and the priority level of source 2 is set as 2, the priority level of source 0 is higher than that of source 2, thus requests of source 0 are firstly responded. After the requests of source 0 have been responded, the priority level of source 0 is reset as 2, the priority level of source 1 is reset as 0 and the priority level of source 2 is reset as 1. In this case, as long as it is determined that source 1 has no request, requests of source 2 will be responded, regardless of the requests of source 0.
3. Polling priority level. As shown in FIG. 4, source 0, source 1 and source 2 are at the same priority level. For example, if multiple tasks are request simultaneously at each source, they will be processed as follows: one task of the source 0, source 1 and source 2, respectively, is output, if tasks of one of the sources, e.g., source 0, have been processed, and source 0 no longer requests arbitration, then tasks of source 1 and source 2 are output next time. Likewise, if source 2 no longer requests output, then requests of source 0 and source 1 are output and arbitrated.
It can be seen from the above description that processing processes of the three arbitration mechanisms are simplex, and can not configure processing modes of the arbitration mechanisms flexibly according to requirements of data. If requests of more sources are required to be processed simultaneously, the processing efficiency will be decreased, and the transportability is not high.